A billiard table or billiards table is a bounded table on which billiards-type games (cue sports) are played. In the modern era, all billiards tables (whether for carom billiards, pool or snooker) provide a flat surface usually made of quarried slate, that is covered with cloth (usually of a tightly-woven worsted wool called baize), and surrounded by vulcanized rubber cushions, with the whole elevated above the floor.:115, 238 More specific terms are used for specific sports, such as snooker table and pool table, and different-sized billiard balls are used on these table types. An obsolete term is billiard board, used in the 16th and 17th centuries.
Cushions (also sometimes called "rail cushions", "cushion rubber", or rarely "bumpers") are located on the inner sides of a table's wooden rails. There are several different materials and design philosophies associated with cushion rubber. The cushions are made from an elastic material such as vulcanized (gum or synthetic) rubber. The chiefly American jargon rails more properly applies to the wooded outer segments of the table to which the cushions are affixed.
The purpose of the cushion rubber is to cause the billiard balls to rebound off the rubber while minimizing the loss of kinetic energy.
When installed properly the distance from the nose of the cushion to the covered slate surface is 1 7⁄16 inches (37 mm) while using a regulation 2 1⁄4-inch (57 mm) ball set.
The profile of the rail cushion, which is the cushion's angle in relation to the bed of the table, varies between table types. The standard on American pool tables is the K-66 profile, which as defined by the Billiard Congress of America (BCA) has a base of 1 3⁄16 inches (30 mm) and a nose height of 1 inch (25 mm). This[clarification needed] causes the balls' rebound to be somewhat predictable during game play.
On a carom table, the K-55 profile is used (with a somewhat sharper angle than pool cushions). K-55 cushions have cloth, usually canvas, vulcanized into the top of the rubber to adjust rebound accuracy and speed.
Finally, snooker tables may use an L-shaped profile, such as the L77 profile. This is mostly[clarification needed] because snooker uses balls of a smaller diameter and smaller pocket entrances than pool does.